Manufacture of large-scale mechanical devices in single-crystal silicon by high-speed grinding

摘要

Abstract: Preliminary studies have been performed on small beams of silicon (1 $MUL 6 $MUL 40 mm) diamond machined by high speed milling/grinding. The effect of the grinding on the strength of these specimens has been assessed by masking a small portion of the surface and etching in a 1:9 solution of hydrofluoric and nitric acids for a set time. Removal of the mask reveals a step which is measured to determine the amount of material removed from the surface. These are then examined using x-ray diffractometry and the etch step surface finish measured using a Rank Taylor Hobson Form Talysurf stylus profilometer. Finally, the strength of the specimens is measured by loading the beams to failure in a small three point bend testing machine and monitoring the failure load. There is a slight increase in strength between the as-ground specimen and those where the surface has been etched by 1 - 2 $mu@m. Both x-ray and stylus measurements indicate the presence of a surface layer of thickness of the order one micrometer that is likely to be due to ductile mode grinding. It is also noted that there appears to be a local peak in strength after approximately 2 - 3 $mu@m has been etched from the surface. This is followed by a small reduction before steadily increasing to a maximum value of 425 MPa. It is speculated that this could be a result of a low defect zone around the tips of the cracks that are invariably propagated during the grinding process.!17